This invention relates to a ladle heating system wherein a lid is applied to the rim of the open top of a ladle, a flame is directed from the lid into the chamber of the ladle and the hot gases are exhausted from the ladle back through the lid. More particularly, the invention relates to a ladle heater for heating a ladle of the type that includes a gate valve in its lower portion and a rod that extends upwardly from the gate valve through the open top of the ladle.
In the molten metals industry, ladles and similar metal receivers such as tundishes and torpedo cars receive a charge of molten metal and transport the molten metal to a casting machine, etc. The receivers usually are lined with a refractory material, and it is desirable to preheat the receiver before molten metal is received therein in order to avoid interface solidification of the metal upon contact between the metal and the interior surface of the receiver, and also to avoid thermal shock to the refractory liner of the receiver and the resulting deterioration of the liner. A preheated ladle also minimizes the heat loss from the molten metal as the metal is transported in the ladle from the furnace to the pouring position, thereby assisting in maintaining the molten metal at a high enough temperature for use in a casting machine or a mold.
A common prior art method for heating ladles and other molten metal receivers prior to charging them with molten metal was to direct an open natural gas flame into the vessel. The open flame heating method permitted combustion gases from within the ladle vessel to escape to the surrounding atmosphere, thus permitting a substantial amount of the heat energy to escape without effective use thereof.
More recently, ladle heaters have been developed which tend to reduce the amount of heat that is permitted to escape to the surrounding atmosphere. For example, U.S. Pat. No. 4,229,211 discloses a ladle heating system wherein a seal is applied to the rim of the ladle and the air/gas stream is preheated in a heat exchanger by the gases exhausted from the ladle through the lid.
While the structure of the above-noted patent is effective in conserving energy during the preheating of ladles, the system does not provide a means for preheating ladles of the type that have a slide gate at the bottom and a stopper rod that extends upwardly from the slide gate through the open upper portion of the ladle. The presence of the stopper rod prevents the prior art lid assemblies from moving into sealing engagement with respect to the rim of the ladle.